-LRB- CNN -RRB- -- Hewing to Obama administration desires , Senate Banking Committee Chairman Tim Johnson forcefully repeated Thursday what he had already said in as many words -- his committee wo n't seek new sanctions on Iran for the time being , and no one else should either .

Administration officials have publicly tried to talk lawmakers down from acting on legislation that would impose even delayed sanctions on Iran during the first phase of a November agreement to curb the Middle Eastern nation 's nuclear program in exchange for relaxed sanctions .

Johnson , D-South Dakota , said Thursday he supports strong sanctions against Iran and has legislation adding new sanctions ready to move should Iran fail to meet its obligations under the deal , which is meant to prevent it from acquiring a nuclear weapon .

`` In the meantime , we should not do anything counterproductive that might shatter Western unity on this issue -- we should make sure that if the talks fail , it was Iran that caused their failure , '' Johnson said in remarks prepared for a Banking Committee hearing on the issue Thursday .

Despite Johnson 's insistence , other lawmakers have n't given up on the idea of sanctions .

A bipartisan group of senators is close to an agreement on tougher sanctions , CNN reported Tuesday , but it is not clear whether the Democratic majority would bring such a deal up for a vote .

That deal , if it comes together , would include a new round of sanctions to begin in six months and would bar the enrichment of uranium . It would permit commercial nuclear power as long as the international community monitored it .

The bipartisan group includes Democrats Chuck Schumer of New York and Robert Menendez of New Jersey and Republicans Lindsey Graham of South Carolina and Mark Kirk of Illinois -- all strong supporters of Israel , whose government has panned the deal as a historic mistake .

`` We see today that that the Iranians are launching a rocket next week , and though this was supposedly made as their space program , it 's well known that this is just a cover for military ballistic weapons program , '' Menendez said at Thursday 's hearing . `` I think that a provocative action in the midst of such negotiations should be interpreted as a sign of bad faith , and only reaffirms in our mind why we need to proceed with some efforts here . ''

But Wendy Sherman , undersecretary of state for political affairs , testified at Thursday 's hearing that while there 's good reason to be skeptical of Iran , it 's important to hold fast with other nations who helped negotiate the deal .

`` Now that we have this first step agreed to , and are about to begin negotiations on the comprehensive agreement that we all want , if we indeed say , ` Well , we did n't really mean it , we 're going to now impose additional sanctions that you all will have to live with around the world , ' our partners are likely to say , ` Well , wait a minute here , you 're changing the rules ; we agreed to harm our own economies in service to diplomacy , and you 're not giving diplomacy a chance . ' ''

` Lack of faith '

Sherman 's comments echoed those of her boss , Secretary of State John Kerry , who told lawmakers Tuesday that U.S. legislation imposing sanctions could give the administration 's international partners in the Iranian nuclear deal -- Russia , China , the United Kingdom , France and Germany -- the wrong idea , even if the bill includes a six-month waiting period to see if the interim agreement succeeds .

`` Even if the sanctions are not imposed , it implies a lack of faith in the process and an unwillingness to play by the rules that our partners are playing by , '' Kerry said .

`` You can design them , we can sit here and be ready to go . We 're just saying to you please give us the opportunity to negotiate along the contours of what we have agreed upon . ''

In his statement Thursday , Johnson agreed to do just that , and suggested that other lawmakers should follow suit .

`` Ultimately , while some of us might differ on tactics , it is clear we all share the same goal : to ensure that Iran does not achieve a nuclear weapon , and to do that diplomatically if possible , while recognizing that other alternatives remain on the table , '' he said .

`` Now that Iran has come to the table and entered into this first step agreement , I believe this may well be the last best chance to resolve this crisis by diplomacy , and so the President is absolutely right to fully test Iran 's leaders , '' Johnson said .

Iranian Foreign Minister Javad Zarif said Monday the deal is off if new sanctions are imposed .

About the deal

Among other things , the deal requires Iran to limit how much it enriches uranium , a step that boosts the concentration in raw ore of a specific kind of uranium isotope that is best suited to maintaining nuclear reactions .

Fuel for nuclear power requires 5 % enrichment , but Iran has stockpiles of uranium enriched to 20 % . That 's not enough for a nuclear weapon but still worrying to international experts who have cast doubt on Iran 's previous assertions that its nuclear program is for purely peaceful purposes .

The initial agreement limits enrichment to the 5 % level and requires Iran to dilute half of its stockpile of 20 % enriched uranium to at least 5 % and convert the rest to a form that ca n't be further enriched by the end of the six-month deal .

The country is also forbidden from turning on additional machines used in enrichment , and must submit to what Kerry has described as `` unprecedented international monitoring '' of its nuclear program .

New designations issued

On Thursday , amid the debate about imposing new sanctions , the administration listed a dozen companies and individuals for helping Iran evade existing sanctions and for providing support for its nuclear program .

They include companies and individuals involved in prohibited Iranian crude oil transactions as well as firms and people who helped Iran acquire parts and technology for its nuclear program .

The designations show the administration 's resolve to enforce sanctions during the six-month interim agreement with Iran , Undersecretary for Terrorism and FInancial Intelligence David Cohen said in a statement .

`` Today 's actions should be a stark reminder to businesses , banks and brokers everywhere that we will continue relentlessly to enforce our sanctions , even as we explore the possibility of a long-term , comprehensive resolution of our concerns with Iran 's nuclear program , '' he said .

In a briefing with reporters , a senior administration official put it more succinctly .

`` We have n't let up ; we wo n't let up , '' the official said .

CNN 's Tom Cohen contributed to this report .

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NEW : Sen. Robert Menendez cites Iranian missile launch plan in calling for new sanctions

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NEW : Administration officials testify that now 's not the time

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Administration worries sanctions bill could derail historic Iran nuclear deal

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Secretary of State John Kerry has pleaded for time to work through the deal